The functional demands placed on modern integrated circuits have resulted in an ever-increasing demand for input/output (I/O) connections to the die. Hundreds of I/O connections are not uncommon. Commonly-owned, co-pending U.S. patent application Ser. No. 916,328 ("parent case"), discussed below, discloses a method for increasing I/O connections for an integrated circuit (die) of a given area. There remains a similar problem with the number of connections required in the package mounting and connecting to the die. Generally, there is a one-to-one correspondence between the number of package connections and the number of bond pads on the die.
Thus, there is a need for semiconductor packaging techniques that can accommodate increased lead count, particularly suited to the dies discussed in the aforementioned U.S. patent application No. 916,328.
Generally, semiconductor packages are used for (1) enclosing (protecting) a semiconductor (IC) die in some kind of package body, and (2) providing external connections for connecting the packaged die to external systems. Packaging the integrated circuit, requires at a minimum, (1) a conductive layer having a plurality of conductive lines, and (2) a "die-receiving area." As is discussed in greater detail hereinbelow, the inner ends of the conductive lines define the die-receiving area.
Once the die is mounted in (on) the die-receiving area, bond pads located on the die will be connected, usually by wire bonding or tape automated bonding (TAB) to inner end portions of the conductive lines.
Generally speaking, there are four distinct techniques of packaging a semiconductor device, in any case said package having one or more layers of conductive lines (leads, traces, or the like) exiting the package for electrically connecting the packaged die to other components, whether by mounting directly to a printed circuit (mother) board or by plugging the packaged device into a socket which in turn is mounted to the mother board. These are:
(1) plastic molding; PA1 (2) ceramic packaging; PA1 (3) PCB-substrate type packaging; and PA1 (4) tape-based packaging. PA1 1. Fitting (fabricating) as many active elements as possible in the active element area, to create more complex devices; and PA1 (1) equilateral triangular shaped dies providing 14% more I/O than a square die of the same size (area); PA1 (2) right isosceles triangular shaped dies providing 21% more I/O than a square die of the same size (area); PA1 (3) 30.degree.-60.degree.-90.degree. right triangular shaped dies providing 28% more I/O than a square die of the same PA1 (4) "Greatly Elongated Rectangular" shaped dies providing 16% more I/O than a square die of the same size (area); and PA1 (5) Parallelogram shaped dies providing 14% more I/O than a square die of the same size (area).
Plastic molding typically involves a relatively rigid lead frame, wherein the lead frame has a patterned layer of conductive leads (conductive lines), the inner ends of which define the die-receiving area. A die is mounted to a die paddle, within the die-receiving area, and is connected to inner end portions of the conductive leads. The die and inner portion of the lead frame are encapsulated by plastic molding compound. Outer end portions of the conductive leads extend outside of the molded plastic body.
Ceramic packaging typically involves one or more layers of conductive traces (conductive lines) applied on interleaved ceramic layers. Again, the die-receiving area is defined by the inner ends of the conductive traces. Outer layers are typically ceramic. The die is mounted in a cavity (either up or down), connected to inner ends of the traces, and the cavity is closed by a lid. Outer ends of the traces are connected, within the ceramic, to external pins or leads (for example) on the exterior of the ceramic package body.
PCB-substrate type packaging involves a patterned layer of conductive traces (conductive lines) on a printed circuit board (PCB) substrate, and the inner ends of the conductive traces define the die-receiving area. The die is mounted to the substrate, connected to the inner ends of the traces, and may be encapsulated by epoxy, plastic molding compound, or in any suitable manner. Outer ends of the traces are connected to external pins or leads (for example), in a manner similar to ceramic packaging.
Tape-based packing involves a relatively non-rigid foil of conductive leads (conductive lines), supported by a plastic layer, and the inner ends of the conductive traces define the die-receiving area. A die is mounted to the substrate formed by the layer of conductive leads and plastic, and is connected to the inner ends of the conductive leads. Outer ends of the leads are connected to (or form) external interconnects for the packaged die.
In any of these, or other, packaging techniques, a die connected to conductive lines and having some sort of support and/or package body is referred to as a "semiconductor device assembly".
FIGS. 1A and 1B show two similar prior art layers 100, 100' of pattered conductive lines, which are applicable to any of the aforementioned package types. A "die-receiving area" 110, 110' is defined by the inner ends 108, 108' of a plurality of conductive lines 106, 106'. A die 102, 102' is mounted in the die-receiving area 110, 110', and bond pads 112, 112' on the die are connected to the inner ends of the conductive lines. Two techniques for attaching a die to conductive lines are shown. In FIG. 1A, the die 102 is wire bonded to the conductive lines 106, as indicated by bond wires 114 extending between the bond pads 112 and the conductive lines 106. In FIG. 1B, the die 102' is connected to the conductive lines 106' by tape automated bonding (TAB) techniques (indicated by 114'). Both of these techniques are well known. Other techniques (not shown) of connecting a die to a pattern of conductive lines include flip-chip and the like.
Notably, as shown in FIGS. 1A and 1B, the die is square. The conductive lines extend (radiate) from the die-receiving area, outward from the die. Hence, a sub-plurality of conductive lines are disposed on each of the four sides of the die, their inner ends defining a square die-receiving area. Also shown, by way of example, in FIGS. 1A and 1B are die attach pads 104, 104', which are generally somewhat larger than the die and somewhat smaller than the die-receiving area.
The conductive lines (106 and 106') include, but are not limited to, lead frame leads, tape leads, and traces on a ceramic or PCB substrate. Ultimately, a package body (not shown) may be formed about the die and inner portions of the conductive lines, as discussed above.
As a practical matter, the number of conductive lines (106 and 106') is determined by the number of bond pads (112 and 112') located on a given die (102 and 102'). A problem with the prior art is insufficient number of conductive lines (106 and 106').
Commonly owned, co-pending application Ser. No. 916,328 provides a technique for increasing the number of I/O bond pads for a given die. Hence, it is desirable to provide an increased number of conductive lines, defining a die-receiving area and connecting to the die bond pads, hence increasing the number of I/O connections.
Therefore, problems with mounting a die within a prior art square die-receiving area is the limitation placed on the number of conductive lines (106 and 106') defining the prior art square die-receiving area (e.g., 110 and 110'). Prior art inner ends (108 and 108') of conductive lines (106 and 106') make up a square die-receiving area, hence, providing I/O connection limited to the periphery of the square. Moreover, the prior art square die-receiving area does not accommodate the increased number of I/O connection on a given die provided in commonly owned co-pending patent application Ser. No. 916,328. Hence, what is needed is (at least) a layer of conductive lines defining a die-receiving area that provides an increased number of conductive lines, thus increasing the number of I/O connections.